Transparent electrodes are used for various devices in a variety of fields. For example, transparent electrodes are used for flat panel displays such as thin film transistor-liquid crystal displays (TFT-LCDs), plasma display panels (PDPs), and organic light emitting diode (OLED) displays; touch panels; electromagnetic shield films; antistatic films; heat reflection films; flat heating elements; and photoelectric transducers.
Transparent electrodes are usually formed of indium tin oxide (ITO). However, if transparent electrodes formed of ITO are used in flexible devices, the transparent electrodes may easily be fractured in the case that stress is applied thereto, due to, for example, strain or bending. Furthermore, since the indium component of ITO is relatively expensive and stocks thereof are being exhausted, it is necessary to find an alternative material.
As a result, techniques for forming transparent electrodes using conductive polymers are gaining attention. Since conductive polymers can be used in various fields such as fuel cells, displays, actuators, antistatic conductive coatings, and electromagnetic shield conductive coatings, a great deal of research has been conducted into conductive polymers. Particularly, a large amount of academic and industrial research has been conducted into conductive polymer patterning techniques for forming thin film transistors or wiring electrodes in flexible displays, considered to be next generation displays.
As a conductive polymer patterning technique, a high-speed solution process for printing on a flexible support using an inkjet printer has recently been developed. FIG. 1 illustrates a conductive polymer patterning technique of the related art using an inkjet printer. According to the conductive polymer patterning technique of the related art illustrated in FIG. 1, droplets are uniformly ejected onto the entire region of a pattern. Such a solution process using an inkjet printer is advantageous in that a desired pattern can be rapidly formed without generating waste and having to use an optical mask. However, a pattern formed by such a solution process of the related art may easily be seen due to the light transmittance difference between a conductive polymer pattern region and the remaining region, to lower the visual quality of a display or a touch sensor.
To address this limitation, the thickness of a conductive polymer pattern may be reduced to lower the light transmittance difference. However, in this case, the electrical conductivity of the conductive polymer pattern is also lowered in proportion to the thickness of the conductive polymer pattern.